The present invention relates to video display and viewing apparatus and methods, and more particularly to an apparatus for and a method of displaying a stereoscopic pair of images and viewing them in three dimensions.
There have been many attempts to provide three-dimensional video display and viewing apparatus. Most noteworthy of these attempts have been in the television field. In general, it is known that three-dimensional viewing can be provided by simultaneous or alternate display of a stereo pair of images on a video display means such as the raster of a television receiver. A "stereo" pair of images are images of the same object or scene taken from different angles much as the different viewing angles of objects or scenes seen by a person as a result of the spacing between the eyes. The stereo images are displayed on a video display and means is provided whereby the viewer sees only one image of the stereo pair with one eye and the other image with the other eye, consequently seeing the scene in three dimensions.
One technique which has been attempted is to display a stereo pair of images on a video display side-by-side, separated by a vertical line. This technique was believed to be desirable for the reason that such image positioning corresponds to the positioning of a viewer's eyes. In this technique, the viewer employs some device so that he sees only one image with one eye and only the other image with the other eye.
Another known technique is to produce a stereographic display of comingled or superimposed images in different colors on a video display and to provide the viewer with separate colored filters so that he sees one image with one eye and the other image with the other eye.
Still another technique is to display the stereo images alternately or sequentially at high speed and to provide means for the viewer such as high speed shutters so that the viewer sees only one image with the left eye and the other with the right eye.
These prior techniques have not been successful for various reasons. Side-by-side image arragement on a video display constrict the horizontal dimension of the images and reduces the stereoscopic effect. Also, standard video display devices such as television receivers do not include a control or adjustment for horizontal sweep so that the image widths cannot be adjusted. To provide for such adjustment would require extensive future modification of such video display devices and prevents satisfactory use of currently existing video display devices.
The techniques using comingled display of images of different color and alternate or sequential image display makes special viewing devices mandatory if the display is to be intelligible so that the display cannot be viewed without such devices. Also, the cost of the instrumentation required to reproduce and view comingled or sequential image display makes these techniques commercially unacceptable.
Specific background inventions are disclosed in three recently issued U.S. patents and are discussed in the following: U.S. Pat. No. 4,523,226 issued on June 11, 1985 to L. Lipton et al and U.S. Pat. No. 4,562,463 issued on Dec. 31, 1985 both describe a stereoscopic television system involving sequential display of the left eye view and the right eye view. The first shows a stereoscopic pair of images disposed one above the other, but with vertical foreshortening of the subject (anamorphic distortion). To overcome this defect, the sweep rate is then increased to twice that of accepted broadcast standards which immediately destroys compatibility with existing practice or equipment used for transmission or reception in the home. Both patents incorporate electronic storage of sequential television fields and require electronically activated polarizers to alternately blank the left and right eye views in synchronism with the television display. As a result, that system is very expensive, limited in application and is also incompatible for viewing without the synchronized polarizing shutters.
U.S. Pat. No. 4,582,393 was issued on Apr. 15, 1986 to David M. Shieman and claims the use of Fresnel prisms and polarizers for viewing "a pair of right and left stereoscopic images of a subject positioned in a side-by-side array." No claim for over and under positions of the images is made, although depicted in one of the drawings, and no preference is stated as to which should be the left eye view. Shieman fails to teach that the upper image should be the left eye view in order to be compatible with 3-D motion picture formats and also to achieve enhanced stereo through motion parallax when using a television camera for live transmission and/or recording for subsequent viewing. Moreover, he uses a prism in front of each eye which introduces combined color shifts, loss of resolution and unnecessary complications in adjusting the deviation angles to accommodate different viewing distances from the display. He proposes interchangeable prisms to provide said adjustment which is far more expensive and cumbersome than the use of a continuously variable optical element.